Fiber rolls, also known as straw wattles, wattles, erosion control rolls, fiber logs, or sediment logs, are a well-known best management practice (BMP) for controlling sediment and erosion caused by storm water runoff. Typically, fiber rolls are tube-shaped structures filled with biodegradable fibrous material, such as straw, rice, flax, coconut fiber material (coir), excelsior (shredded wood), or composted material. The fiber rolls may be wrapped and held together with geotextile fabric, such as burlap, jute, or coir, or UV degradable plastic netting. Fiber rolls can be used in a variety of sloped settings to reduce the erosion effects of long or steep slopes in a variety of landscaped sites.
Fiber rolls are designed to allow for water flow, while filtering and capturing sediments and debris. In so doing, fiber rolls may be used to direct and/or slow water velocity and diffuse overflows, thereby reducing rill and other types of erosion that may occur with uninterrupted water flow down a sloped surface. They also help to trap and settle out sediments, thereby keeping soil onsite and reducing sediment loads to storm drain systems and receiving waters. Additionally, fiber rolls may capture seeds present in stormwater and allow the seeds to settle and germinate. In this way, fiber rolls may promote the growth of plants and natural vegetation.
Historically, silt fences have been used as an alternate method of controlling erosion along slopes. Silt fences are generally constructed of black porous cloth (e.g., geotextile cloth) strung vertically on wooden stakes across a slope to capture sediment. As known in the art, silt fences are usually labor intensive to install and remove. They also may be discouraged because of the propensity for silt fences to collapse and fail, for instance when they encounter high fluid flow or high winds.
Fiber rolls have been found to be an effective alternative erosion control solution. They may be installed in projects with slopes, minimal slopes, or on flat ground to keep sediment from washing onto landscaped areas, such as sidewalks or streets, and into storm drains. For example, fiber rolls may be placed around storm drains to reduce the effects of sediment pollution. They may also be placed along sidewalks to prevent sediment from washing into gutters.
Proper installation of fiber rolls, however, is needed to ensure effective slope protection. In a typical installation along a hill, multiple fiber rolls may be placed in rows substantially perpendicularly to the slope; in effect, shortening the slope length. The vertical spacing of each row is dependent on the slope gradient. Wooden stakes typically are driven through the fiber roll, for example, perpendicular to the slope face, to secure the fiber roll. In an alternate installation, the conventional stakes are placed to the side of each fiber roll, and one or more ropes may be secured to the stakes to secure the rolls. For example, one or more ropes may be interwoven between alternating stakes placed above and below the fiber rolls. The resulting system of fiber rolls is designed to reduce soil erosion and to dam, direct, and/or filter stormwater flowing down the slope.
When more than one fiber rolls are placed end-to-end in a row, there is the possibility of focused water and sediment leakage at the abutments. Gaps at the ends of adjacent rolls may provide a focused pathway for runoff to concentrate, which can accelerate erosion. For this reason, some regulatory agencies require that the ends of adjacent fiber rolls tightly abut or overlap. For instance, the end of a fiber roll may be overlapped over the end of an adjacent fiber roll to minimize the water velocity at the ends of the rolls. The amount of overlap depends on the requirements of a particular site and/or agency. As an example, a particular site may require that the end of each erosion control roll overlap with one to three feet of the adjacent roll.
This configuration requires additional material in the form of additional fiber roll length needed for a given site. It may often involve additional labor to secure the ends of each fiber roll, either to ensure a firm abutment or to create a sufficient overlap to minimize leakage at the ends. The configuration may also require additional labor to adequately secure overlapped fiber rolls to the sloped surface. It can also increase the costs for installing fiber rolls on a particular site.
In addition, when installing fiber rolls using conventional stakes, the stakes must be positioned and driven into the ground with care so that the stakes are sufficiently driven through the fiber roll to secure the roll in place but are not broken in the process. In some instances, heavy sediment loads could pull the fiber roll off the stake if the stake is driven down too low. Moreover, conventional stakes are usually driven through the fiber rolls and into the ground, with the top of portion of the stake remaining exposed. The exposed stake ends pose a potential safety hazard, particularly in areas with or near foot traffic, such as sidewalks and parking lots.
While many current regulations allow biodegradable fiber rolls, such as those made of straw and covered in burlap material, to be left in place after construction activities have been completed, the stakes must be removed as they may create a safety hazard to ongoing landscape maintenance operations. The use of conventional stakes in these applications thus requires additional time, labor, and resources for maintenance during construction and removal after construction. It can also increase the costs for maintaining and removing fiber rolls on a particular site.
Given their size and above ground positioning along a slope or ground surface, fiber rolls may create an obstruction on the ground surface. As such, they may present a potential safety hazard in construction sites and other landscaped areas, particularly in areas subject to heavy foot traffic.
Accordingly, there exists a need for more effective devices and systems for controlling erosion, including a need for improvements in safely and efficiently installing fiber rolls in landscaped areas.